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Malicious package

css-scroll-state-polyfillnpm

Advisory published Updated

css-scroll-state-polyfill is a confirmed malicious npm package (MAL-2026-17486) that steals credentials and exfiltrates sensitive data (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in css-scroll-state-polyfill (npm)

MAL-2026-17486
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall css-scroll-state-polyfill

What this malware does

The package presents itself as a CSS polyfill but ships a payload file (thunderboltRegistry.js) that executes an IIFE at require time. The IIFE uses child_process to run host-identification commands (id, whoami, uname -a, ifconfig/ip addr, /etc/hosts, hostname) and collects Node version, platform, and PID, then sends the captured data via fetch to a hardcoded webhook.site collector at https://webhook.site/0492a36c-4d7b-408a-865c-226db25987ba. The main index.js is an empty stub; filenames mimic internal Wix Thunderbolt registry modules, consistent with a dependency-confusion squat targeting that namespace. A self-identifying 'beacon=poc15' tag is included in the request. The payload also walks require.cache and deletes any entry whose key contains 'thunderboltRegistry', causing subsequent requires in the same process to re-execute the recon-and-exfiltration path rather than return a cached export, and exports a Proxy that answers arbitrary method accesses to blend in with the impersonated registry.

Malicious versions

1 flagged
1.0.0

Indicators of compromise (SHA-256)

cffa0affc34bac3fa24fcc7c67aae4d120066f4f856cb8b637bc04c6ca9d482c

Detection & response playbook

Credential / info stealer

  1. Find it

    Search your lockfiles and build artifacts for css-scroll-state-polyfill (version 1.0.0).

  2. If you installed it — respond

    css-scroll-state-polyfill is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.

  3. Did it already run?

    If css-scroll-state-polyfill was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. css-scroll-state-polyfill on npm has been identified as a malicious package (version 1.0.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-020895

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks css-scroll-state-polyfill-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Malware detection Runtime egress monitoring

Explore

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css-scroll-state-polyfill (npm) malicious package — MAL-2026-17486 | O3 Security